Gas barrier properties have been hitherto imparted to the surface of a plastic molded body by forming a thin film thereon. Methods of laminating a thin film having gas barrier properties (hereinafter, also referred to as a gas barrier thin film), which contains an inorganic oxide as a main component, on the inner surface of a plastic container using a plasma chemical vapor deposition method (plasma CVD method), have been disclosed (see, for example, Patent Literature 1). However, in regard to a method for forming a thin film by a plasma CVD method, plasma damages the film surface at the time of thin film formation so that the compactness of the film is prone to be impaired, and it is difficult to obtain high gas barrier properties. Furthermore, since a plasma CVD method ionizes a raw material gas by decomposing the raw material gas with plasma, and causes ions that have been accelerated by an electric field to collide with the surface of a plastic container to form a thin film thereon, the method essentially requires a high frequency power supply and a high frequency electric power adjusting apparatus, and there is a problem that a large amount of money is required for the equipment cost.
A method of decomposing a raw material gas by bringing the raw material gas into contact with a heating element that has been caused to generate heat, and depositing the chemical species thus produced as a thin film on a base material directly or after a reaction process in a gas phase, that is, a CVD method which is also called a heating element CVD method, a Cat-CVD method or a hot wire CVD method (hereinafter, in the present specification, referred to as a heating element CVD method), has attracted public attention as a next-generation film forming method, because the method can solve the problems of the plasma CVD method as described above, and can form a compact thin film having high gas barrier properties by using a film-forming apparatus that is simpler and less expensive than the film-forming apparatuses for the plasma CVD method. However, when a silicon hydride such as monosilane, disilane or trisilane is used as a raw material gas, because these compounds have pyrophoricity, expenses are required for safety apparatuses, and the advantage of lower cost compared to the film-forming apparatuses for the plasma CVD method fades away. Thus, the applicant of the present invention has suggested a technology for forming a SiOx thin film or an AlOx thin film on the wall surface of a plastic container by a heating element CVD method, using a highly safe raw material such as a non-pyrophoric raw material as a raw material gas (see, for example, Patent Literature 2).